The present invention relates to a step motor used for an electric timepiece wherein a timepiece hand is moved intermittently every unit time (to be called step movement hereafter).
In a known electric timepiece, when, for example, a second-hand is made to undergo step movement, a step motor, an electromagnetic solenoid and other related structure is generally used. However, the former step motor is generally complicated in construction, and a particular signal such as a two-phase signal is required as the motor input signal. With the latter electromagnetic solenoid, although the input signal is simple, the electric power consumption is very high and this limits its usefulness as a driving device of an electric timepiece wherein a battery is used as the electric power source.
The applicants have previously proposed a driving device as shown in FIG. 1, enabling elimination of the defect mentioned above. In the device previously proposed by the applicants the first rotor and the second rotor make a rotation of 180.degree. at each unit time when effecting a step-movement of the hands. There is, however, a difficulty in using the device, especially for a small-sized clock, in the fact that if the second-hand is step-moved at the above rotation angle, for example, the reduction ratio of a wheel train will become 1:30, resulting in enlarging the second-hand wheel or an intermediate gear wheel, or requiring an extra reduction gear wheel.